feat: Live Tool Call Stream — real-time feed with filtering and pause

[vivekchand]

Closes #31

What

Replaces the cramped 120px live activity feed on the Flow tab with a full-featured Live Tool Call Stream panel that shows real-time tool invocations across all sessions with filtering, pause, and result pairing.

How

UI (both themes):

• 360px scrollable panel with tool call entries showing color-coded tool name badges
• Filter pills: All, exec, read, write, edit, browser, search, message, spawn — click to show only that tool type
• Pause/Resume button: freezes the UI while still buffering incoming events; resume replays them
• Clear button to reset the stream
• Tool result pairing: tool_end events display completion status alongside invocations
• Filter status bar shows active filter and paused state

Backend:

• New /api/tool-calls/recent endpoint on bp_logs blueprint
• Scans the 10 most recent session JSONL files for tool_use/toolCall blocks
• Pairs tool calls with tool results by matching IDs
• Supports ?limit=N and ?tool=<name> query params

JS:

• _toolStreamItems buffer (100 entries max) with toolName, color, timestamp
• setToolFilter() updates pills and re-renders visible items
• toggleToolStreamPause() buffers events while paused, replays on resume
• loadRecentToolCalls() pre-populates the stream from the API on Flow tab init
• extractToolName() parses tool names from log messages
• getToolColor() maps each tool to a distinct color

Tests:

• 4 new tests for /api/tool-calls/recent (structure, limit, filter, field validation)
• All 55 existing tests pass